Sources and Rates of Phosphorus in a Cultivation System Integrating Crop and Pasture Production in the State of Parana

The integration of crop and pasture production (ICP) within the same area, using no-tillage cultivation systems, is becoming popular in Brazil due to its agronomic advantages. Phosphorus is a key nutrient in these systems and soils in the state of Parana are generally low to medium in bioavailable P. The main purpose of this research is to evaluate the effects of P rates and sources (water-soluble and water-insoluble) on soil quality, plant mineral nutrition, forage, grain, and meat yields in an integrated crop-livestock system under no-till. The site has been under no-till for five years. Treatments included three sources of P [triple superphosphate (TSP), magnesium thermophosphate (MTP), and Arad reactive rock phosphate (RP)] and three rates of P (60, 120, and 180 kg total P₂O₅/ha), with all sources applied prior to seeding the winter crop. The trial also included a control, with no P applied, and three treatments supplying each source at 90 kg P₂O₅/ha applied prior to seeding the spring-summer crop.

Results so far indicate that it is possible to obtain high yields of maize and soybean (up to 12 t/ha and 5 t/ha, respectively) by anticipating the P application to the winter forage crop (black oats or ryegrass). Second, besides high grain yields, the anticipated P application leads to animal rate growth of up to 1 kg per day. Third, in the first 2 years, the TSP performed better as related to other P sources. Fourth, in the last year, crop response was higher with the MTP, and fifth, RP has performed as the least effective P source for this system. This project is expected to continue providing more insights until 2015. Brazil-55